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Tremadoc Geol.|trɪˈmædək|
The name of a village in Gwynedd, N. Wales, used attrib. to designate a series of Tremadocian rocks (see next) about 300 metres thick that form the top of the Harlech Dome and comprise mudstones, shales, and slates; also, more widely, = next.
1847A. Sedgwick in Q. Jrnl. Geol. Soc. III. 145 The anomalous position of the Tremadoc rocks,..and the dislocation of the beds above noticed along the Merioneth coast, were probably all produced by the same set of disturbing forces. Ibid. 157 The Festiniog or the Tremadoc group. 1882A. Geikie Text-bk. Geol. 655, 12 species of lamellibranchs from the Tremadoc beds of Ramsay Island and St. David's. 1885C. Lyell Student's Elem. Geol. (ed. 4) xxviii. 448 Mr. Callaway has shown that the Shineton shale of Shropshire is of Lower Tremadoc age. Ibid., Orthoceras sericeum and Cyrtoceras præcox are of the Upper Tremadocs. 1938A. K. Wells Outl. Hist. Geol. iii. 20 The graptolites..had made their first appearance in Tremadoc (Upper Cambrian) times. 1970R. M. Black Elements Palaeont. xiv. 222 Primitive pterobranchs are found in rocks of Tremadoc age. 1974Encycl. Brit. Micropædia X. 108/3 Important Tremadoc sequences are..known from Australia. |